1. Field of the Invention
The present invention relates to electromagnetic wave measuring apparatuses and methods for measuring electromagnetic waves radiated from electronic components. More particularly, the present invention relates to an electromagnetic wave measuring apparatus and method for measuring an electromagnetic field distribution of electromagnetic waves radiated from portable wireless devices such as mobile phones.
2. Description of the Background Art
In recent years, the use of portable wireless devices such as mobile phone has become rapidly widespread on a global scale. At the same time, electromagnetic waves are controlled due to concerns about possible health effects which could result from exposure to an electromagnetic field radiated from a portable wireless device used in close proximity to a human body.
There already exists a technique known as a parallel detection method, which is adopted in an apparatus for measuring a distribution of an electromagnetic field radiated from an electronic device such as a portable wireless device. For example, Japanese Patent Laid-Open Publication No. H9-304456 discloses an apparatus utilizing the parallel detection method. This apparatus has a plurality of micro loop components arranged in lines with respect to an object to be measured, and a plurality of level detection sections corresponding to the micro loop components, thereby concurrently storing and processing signals detected by the micro loop components. With this conventional apparatus, it is possible to measure a two-dimensional distribution of an electromagnetic field of electromagnetic waves radiated from the object to be measured by moving the plurality of micro loop components in a predetermined direction.
Also, an apparatus utilizing the parallel detection method, which is disclosed in Japanese Patent Gazette No. 3163016, adopts a tabular layout of a plurality of loop components arranged like non-parallel sides of a trapezoid with respect to an object (e. g., an electronic circuit substrate) to be measured. With this conventional apparatus, it is possible to measure a two-dimensional distribution of an electromagnetic field of electromagnetic waves radiated from the object to be measured by moving the plurality of loop components.
There also exists a technique known as a sequential selection method, which is adopted in an apparatus for measuring an electromagnetic field distribution radiated from the electronic devices. The apparatus utilizing the sequential selection method, for example, adopts a two-dimensional grid-like layout of a large number of micro loop components, and sequentially selects the micro loop components by a switching diode, etc., thereby processing signals detected by the micro loop components.
In general, the main object of these conventional apparatuses for measuring an electromagnetic field distribution is to measure a two-dimensional electromagnetic field of a low frequency under approximately 1 GHz, which is radiated from an object to be measured such as an electronic circuit substrate.
For example, if the object to be measured includes a three-dimensional electromagnetic wave source of high frequency (e.g., 2 GHz) such as a mobile phone, electromagnetic waves radiated therefrom and an electromagnetic field distribution are also three-dimensional. However, the above conventional apparatuses for measuring an electromagnetic field distribution, in which a plurality of micro loop components are arranged in a two-dimensional manner, are unable to detect a three-dimensional electromagnetic field distribution, which results in poor measurement accuracy.
Also, in the case of the apparatus utilizing the sequential selection method, the micro loop components having a two-dimensional grid-like layout are sequentially selected and processed, whereby enormous amounts of scanning time are required. Furthermore, due to the influence of capacitance between terminals of a switching diode and frequency characteristics of a transmission line, there arises a problem of degradation of sensitivity characteristics and isolation between the adjacent micro loop components at an extra high frequency (for example, 2 GHz).
In the case of the apparatus utilizing the parallel detection method, a scanning time can be reduced by parallel processing of signals detected by a plurality of micro loop components. However, each micro loop component has to be provided with a detection section, which results in an increased cost.